Regular female cannabis plants are photo-sensitive when it comes to flowering. Thus, when the daylight period shortens, or the grow lights are switched to a flowering schedule (12/12), it triggers the cannabis flowering stage. Apart from the best light cycles for flowering stage cannabis plants, it is important to know exactly what to expect. Do remember that autoflowering strains will blossom after a fixed growth period regardless of the light cycle.
There are various signs that tell you about pre-flowering and the first signs of the flowering stage. Once you are familiar with the general signs, you can then refine your observations for the specific strains that you are growing. All strains of cannabis have the same trajectory, from the first signs of the flowering stage to the peak trichome maturity that signals the readiness for harvest. However, the timelines and details vary from strain to strain.
This article covers the general trajectory with some information about the deviations that might occur in some strains. Read on if you want to know about the various phases of the cannabis flowering stage.
What are the first signs of the flowering stage?
A flowering cannabis plant in its first few weeks will exhibit a strong propensity for growth towards the top ends, and it will feel like a sudden growth spurt. At the same time, tiny hair-like projections will start to appear at major nodes on the stem, telling you that you have buds growing on your plants.
If a plant shows signs of growing pollen sacks, that is a sign that it is a male plant. They must be separated immediately. Otherwise, the pollen sacks will eventually open and pollinate the female plants. That will leave you with seeds and low-potency flowers.
First signs of the Flowering Stage: Outdoors
If you are growing outdoors, it is easy to know when your plants will start flowering. The moment the days start to shorten, you can expect the process to begin. As the available daylight falls below 12 hours, the plant will show the initial growth spurt that signifies that it is preparing to bear the heavy flowers.
If you are growing cannabis outdoors, it is very important to cut out any light source that may be leaking into your crop after sunset. This will confuse the plant and cause any number of odd behaviors. It might go back to a vegetative state or it might produce very little bud and that too of low quality.
What Do Buds Look Like When They Start To Form?
The cannabis flowering stage is a gradual process, and you will see the first tell tale white pistils only in the second week. Once these have formed, you can easily tell where the main colas are going to be. From the third week or so onwards, they will start to appear in various places all over the plant, clustering around the topmost points. These clusters will gradually become larger and become full colas of buds.
Below, we have a week-by-week breakdown of the cannabis flowering stage. It will tell you exactly what to expect in each week and how to take care of the plant. We have also included some information about possible deviations from the norm in certain strains.
Week 1 of Flowering Stage
Week 1 is a transition phase that is triggered by the shortening of daylight hours (whether natural or artificially created). This tells the plant to get ready to grow theheavy buds. In response, the structure starts to become stronger and thicker. This is thus a great time to give your crop a final boost through careful planning.
The distinctive odor develops gently around this time, and the plant kicks into an accelerated growth phase. If you do not have fans creating a rippling breeze through your plants, now is a good time to get it going. The air currents will cause the plants to develop thick stems, resulting in bigger yields.
This is also a good time to give your air circulation some thought. Ideally, every indoor grow space should have air intake holes at the lower level with a vacuum extractor set as high up as possible. This creates a positive airflow and maintains the optimum temperature. This will also ensure a higher CO2 presence in the environment, causing them to grow faster and withstand high temperatures.
You can tell that the plant has entered this phase when you notice a sudden increase in growth activity at the tips. The plant will produce new leaves there and will add to its height.
At this point, there are still about 20 days for the plant to perform vegetative growth before switching its energy over to focus exclusively on flowering. Depending on the strain, the growth in the following weeks can be gradual or exponential. Either way, it will need more space to grow. So make sure there’s room for that.
You can now start to provide some bloom feed along with your main growth feed. The ratio will gradually shift, and you will switch to bloom feed only by the fourth week.
This is also a good time to do some LST (low-stress training). Bend the stems away from the center of the plant to achieve an evenly distributed canopy that allows more efficient light utilization and thus achieves a larger yield.
You may also consider pruning some of the leaves up top if the plant is extra bushy. This is done to allow more light to reach the lower parts of the plant. This must be done carefully so that you do not stress the plant and thus lower your yield or cause irreversible damage.
Early Cannabis Flowering Stage Temperature and Humidity
During the first few weeks, till about the third week, the ideal temperature ranges between 68-77°F or 20 to 25°C. and the humidity should be down to about 40-50%.
Also, these are settings meant for indoor growers who can exercise precise control over their environment. Outdoor On the other hand, growers will simply need to time their sowing carefully so that the harvest happens during optimum weather conditions.
Week 2 flowering stage
As week 2 rolls in, white hairs/pistils appear in places where the big fan leaves meet the stems. These are the building blocks of the larger buds that form the colas. You can tell that the plant has gotten into the flowering phase. This is a good time to examine your stress training strategy and make adjustments based on the plant’s growth.
Continue to administer the growth nutrients at least once a week as the plant is still growing to accommodate the big colas that are to come. The flowers are still very small but they are increasing in number and size every day. So you should also increase the flowering nutrients because the flower growth will only accelerate from this point on.
Enzymes administered every two weeks, starting from week one, are a great way to clean out dead roots and prevent salt build-up. This results in stronger, healthier plants and a larger, high-quality harvest.
Week 3 flowering stage
At this point, the white hairs start to grow in unison, with the buds clustering and starting to look like the colas they will grow into together. The plant is much larger now than how it was three weeks ago. It may increase by as much as 50% of its original size. The odor hasn’t become pungent and obvious yet because the resin glands and trichomes haven’t kicked in. However, the smell has definitely changed and become more apparent.
Check the dosage instructions from the nutrient manufacturers to understand how to balance flowering and growth nutrients. The plant is still growing in the third week, so it will need some feeding for growth. At the same time, this is when the energy is slowly being shifted to producing the buds, so flowering nutrients are very important.
A good balance can be achieved through careful observation and prior experience with the strain and growing environment. Trust your own observations along with what the labels tell you. Always err on the side of underfeeding.
Defoliation During Marijuana Flowering Stage
Defoliating cannabis is the technique of gradually removing leaves to allow the plant to spend more of its energy on the flowers. This is a high-stress technique because you are essentially removing the power sources of the plant. So it is important to understand how to do it correctly.
A lot of growers tend to defoliate at the end of the third week when the vegetative growth has maxed out. As soon as the flowering stage starts, you will have about three weeks during which the plant will grow exponentially. With adequate nutrition and careful pruning, you can direct the plant’s attention towards the areas where the bud production will be maximum. This is usually at the top ends and where there is the most light and air. So you can defoliate gently from the bottom and then do most of the pruning at the end of the third week.
Start to remove fan leaves from the bottom up, where there is the least bit of light, and start to move upwards. Do this gradually over days and weeks instead of suddenly one day. The sudden loss of a lot of all its fan leaves will shock the plant and might even kill it. Dng defoliation in late flowering is not a good idea because the plant may not receive the energy it requires to grow the buds. So it is all about strategy and understanding your plant. Practice this before trying it on a large crop. Every grower tends to develop their own rhythm and preferences over time for defoliation.
What about if I am growing an autoflower – Can I still defoliate?
Defoliating is a technique that is mostly used on photoperiods, however you can defoliate autoflowers too but it is slightly more risky due to the shorter vegetative and flowering stages which may not always allow enough recovery time from high stress techniques.
Week 4 Flowering Stage
This is where the bloom-only phase of the plant begins. The plant has now achieved its final height and size and will not grow any further. So you can discontinue growth nutrients and continue to feed your plants with only bloom/flowering nutrients.
Pay close attention to your plants and look for signs of overfeeding, underfeeding, nutrient burns, and deficiencies.
If you have done LST-based shaping of the plants along with super cropping techniques for more distributed foliage, this is when your hard work starts to pay off. Thanks to the greater availability of light, air, and an overall larger structure, you get multiple large colas instead of one or two big ones.
Week 5 flowering stage
The flowers start to develop at a fast pace now. This is when you need to provide high amounts of phosphorus and potassium. Nitrogen can now be cut back entirely in most cases, but it varies from plant to plant. Knowing your strain and your individual plants is key. Always observe how they are growing and responding to nutrients.
You can also easily administer nutrients via the leaves by spraying them. This will speed up the nutrient uptake and leave the soil pH levels as is. It is also a great way to understand how your plant is responding to feed and check for deficiencies and excess.
How big should buds be at 5 weeks?
Some varieties might explode between the third and fifth week, but usually, the buds will continue to develop well into the eighth week.
So it largely depends on your plant and strain. That said, you should be able to clearly make out the main colas, and the clustering should be fairly thick by now, even if the size is still growing.
Week 6 flowering stage
By the sixth week, you have officially entered the late flowering stage. This is when you can consider some final pruning and nutrition checks. The colas will be mostly mature and they will have grown close to their final size. The odor should be fairly strong around this time, and the buds will be growing every day. You might find newer, smaller buds developing even around this time. You can decide whether you want to keep them or prune them away so that the plant can focus on the main areas.
Continue to follow your nutrients manufacturer’s label for guidance but always look at your plant’s response to know exactly how much to feed. Again, erring on the side of underfeeding is wise.
This is also a good time to start checking your trichomes for development. Keep an eye out for any bugs, mold, etc., that might have escaped your notice. There’s still time to fix these issues and attain a good harvest.
Week 7 flowering stage
At this stage, it is good to reduce the lighting hours further and give your plant more dark hours. This mimics the natural progression of the daylight hours in nature, and the darkness helps the flowers mature better and faster. 13 off and 11 on is a good cycle, and some growers even recommend longer dark periods. You can also look at how your plant is behaving, and based on the experience of previous harvests, you can continue to tweak this to suit your strains.
Doing some research into the lineage of your strains will tell you where the parents originate from. It will give you clues as to how your strain might be best helped in terms of changing the atmospheric conditions and even nutrients.
This is the right time for flushing your plants. it is the process of clearing the soil of all nutrients so that the plants cannot draw anything through their roots. As a result, they will proceed to do something that is similar to autophagy in humans. It will cannibalize its own fan leaves to supply nutrients to the flowers. This should only be done when you are confident that the harvest is just about two weeks away.
This technique works well to extract all the nutrition that is trapped in the leaves, leading to cleaner smoking and higher-quality buds. When this is done late into the flowering stage, it causes the plant to essentially feed upon itself. You will NOT be adding more nutrients after flushing.
There are special rinsing solutions that are used for flushing, but you can also just use plain water and do it gradually. Then when you water your plants, you should only provide them with zero ppm RO water which has no nutrients at all in it. This ensures that the soil stays “flushed”, forcing your plants to draw the nutrients from the leaves.
The leaves will start to fade out, turning yellow and then falling off. So your ripe buds should have fall colors of yellow and orange.
Remember that flushing may not combine well with extreme defoliation. With no leaves left to draw nutrients from and nothing left in the soil, the plant will simply starve to death. So learning how to balance these two techniques is key.
Late Cannabis Flowering Stage Temperature and Humidity
Assuming that your harvest is about two weeks away, this is the time to change the temperature and humidity to the optimum levels for the late cannabis flowering stage. The temperature should ideally be around 18 to 24°C or 64-75°F. The humidity levels should also be brought down to around 30-40%.
Most expert growers formulate their own set of temperature and humidity levels for each phase of the cannabis flowering stage. So you will notice that these numbers tend to vary by a few to several degrees depending on who you ask. It also varies based on the environment, equipment used, etc.
Week 8 -10 Flowering Stage Onwards
At the end of the seventh week, you can start to switch on your UVB lamp towards the end of each day to mimic natural daylight conditions during the normal flowering season. This is an additional technique for enhancing the flavor profile and potency of the buds. It is optional, but it really helps with terpene production, giving your buds a beautiful bouquet of diverse aromatic compounds.
Your buds growing into full maturity will release beautiful aromas and make their presence felt. There will be that heady feeling to it if the growth has been successful in all aspects.
This is usually the final week of the marijuana flowering stage. Some plants might take a few more days to mature fully and thus go into the ninth week. At this time, it is good to give it another extra hour of darkness, thus switching to a 14-off, 10-on cycle. The UVB can continue to come on at the end of the day.
If you have performed flushing, the plants are still fasting and the fan leaves are fading and falling off. Keep checking the trichomes to know exactly when your plant is ready for harvest. The optimum time is when all trichomes are cloudy and some have started to go amber. Make sure you are looking all over the plant, down to the innermost buds, and not just the main colas.
As the eighth week ends, you are approaching harvest. It is a whole other process that requires a lot of care and precision. If you have taken care of your plants through the flowering stage, you now have big, heavy, beautiful buds ready for harvest. Overall care and attention will result in fragrant, potent, and therapeutic marijuana flowers with diverse cannabinoids and terpenes, resulting in a smooth smoking or vaping experience.
Check our article on trimming your buds post-harvest to know all about dry, wet, and machine trimming plus best practices.